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__Physical
Quantities:__

__Physical Quantities:__

In physical science, we commonly deal with quantities such as

**etc. These quantities are known as**__pressure, volume, mass, temperature, current,__**. A physical quantity has two components, namely,**__physical quantities__**and its**__numerical value__**and is written as**__unit____Physical quantity__**=**(Numerical value)**(unit)**__Examples :____Force__= 5**Newton**Here Physical Quantity is Force and its Numerical value**5**and units Newton.

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- 1. C.G.S. Units:
Physical Quantity → Name of Unit → Symbol

Length → Centimeter → cm

Mass → Gram → gm

Time → Second → s

Electric current → Ampere → amp

Temperature → Kelvin → °K

Physical Quantity → Name of Unit → Symbol

Length → Centimeter → cm

Mass → Gram → gm

Time → Second → s

Electric current → Ampere → amp

Temperature → Kelvin → °K

Length → Centimeter → cm

Mass → Gram → gm

Time → Second → s

Electric current → Ampere → amp

Temperature → Kelvin → °K

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__1. S.I. Units:__
**Physical Quantity → Name of Unit → Symbol**

**Length → Meter → m**

**Mass → Kilogram → Kg**

**Time → Second → s**

**Electric current → Ampere → amp**

**Temperature → Kelvin → °K**

__1. S.I. Units:__**Physical Quantity → Name of Unit → Symbol**

**Length → Meter → m**

**Mass → Kilogram → Kg**

**Time → Second → s**

**Electric current → Ampere → amp**

**Temperature → Kelvin → °K**####
__Dimension of Physical Quantity:__

Dimension of Mass = **M**

Dimension of Length = **L**

Dimension of Time = **T**

__Dimension of Physical Quantity:__
Dimension of Mass =

**M**

Dimension of Length =Dimension of Length =

**L**

Dimension of Time =Dimension of Time =

**T**####
__Derived Units and Dimension From its Basic Formula:__
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__Area:__

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Area = Length × Length

Thus the unit of Area = Unit of Length × Unit of Length

Unit of Area in C.G.S. System is **cm²**

Unit of Area in S.I. System is **m²**

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** **

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__Derived Units and Dimension From its Basic Formula:__####
__Area:__

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Area = Length × Length

Thus the unit of Area = Unit of Length × Unit of Length

Unit of Area in C.G.S. System is **cm²**

Unit of Area in S.I. System is **m²**

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__1. Force:__

From the Newton Second Low of Motion,
Force = Mass × Acelaration
or, Force = Mass × Velocity/Time
or, Force = Mass × (Length/Time) /Time
or, Force = Mass × (Length/Time²)
Thus the unit of Force in C.G.S. System,
= Unit of Mass × (Unit of Length/Unit of Time²)
= gram × (cm/sec²)
= gram cm/sec² or gram cm sec⁻²
or __Dyne__
__Again in the same way Unit of Force in S.I System,__
= Kg m/sec² or Kg m sec⁻²
or __Newton__
From the above discussion dimension of Force,
= dimension of Mass × (dimension of Length/dimension of Time²)
Thus the dimension of Force = [M L T⁻²]

__1. Force:____Dyne__

__Again in the same way Unit of Force in S.I System,__

__Newton__

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- Conservation of 1 Newton to 1 Dyne :

1 Newton = 1 Kg m/sec²
= (1Kg × 1 m )/1 sec²
We know that, 1 Kg = 10³gm and 1 m = 10² cm
Thus, 1 Newton = (10³gm × 10² cm)/1 sec²
= 10⁵ gram cm/sec²
= 10⁵ Dyne
__2. Work:__

We Know that,
Work (W) = Force(F) × Displacement(d)
Thus, the unit Work = unit of Force × unit of Displacement(d)
So the Unit of Work in C.G.S. System,
= (gram cm/sec²) × cm
or gram cm²/sec² gram cm² sec⁻²
or __erg__
And the unit of work in S.I. system,
or Kg m²/sec² Kg m² sec⁻²
or __Joule__

__2. Work:__

We Know that,

Work (W) = Force(F) × Displacement(d)

Thus, the unit Work = unit of Force × unit of Displacement(d)

So the Unit of Work in C.G.S. System,

= (gram cm/sec²) × cm

or gram cm²/sec² gram cm² sec⁻²

or

__erg__
And the unit of work in S.I. system,

or Kg m²/sec² Kg m² sec⁻²

or

__Joule__####
From the above discussion dimension of Work,
= dimension of Mass × {(dimension of Length)²/dimension of Time²}
Thus the dimension of Work = [M L² T⁻²]

__Conservation of 1 Joule to 1 erg :__

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1 Joule = 1 Kg m²/sec²
= (1Kg × 1 m² )/1 sec²
We know that, 1 Kg = 10³gm and 1 m = 10² cm
Thus, 1 Joule = {10³gm × (10²)² cm}/1 sec²
= 10⁷ gram cm²/sec²
= 10⁷ erg

- Energy :

The ability to doing work is termed as Energy.
__Thus, the unit and dimension of energy and work is same.__

Unit of Energy in C.G.S System is erg and S.I. System is Joule.

- Energy :

The ability to doing work is termed as Energy.

__Thus, the unit and dimension of energy and work is same.__

Unit of Energy in C.G.S System is erg and S.I. System is Joule.